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Towsey

Strelok advice please

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Hi all

 

I've got the standard free strelok on my android phone and although it's good for my .22lr I can't get much joy with it with my .17hmr. I know I'm not off to the best start because my reticle isn't on the app (hawke half mil dot) and I have no access to a chrono to put velocity in accurately but it's about spot on with the 22 anyway but not very close at all really for the 17, ive played with some bits to sort of average it out but it's not rite.

 

I'm due a new phone very soon so I was going to buy either strelok plus or pro but I don't know if my reticle is on either or both of them or even wot the differences are between the three apps?

 

Any help, advice or even tips and tricks to get it right would be very gratefully recieved

 

Many thanks

 

Towsey

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Reticle should be on all of them. If you get pro put as much info in as you can then to get bullet speed use the trajectory validation button.

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What do you get with pro that you don't get with iStrelok? Also how do they compare with Applied Ballistics app (which is more expensive still)

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What do you get with pro that you don't get with iStrelok? Also how do they compare with Applied Ballistics app (which is more expensive still)

I have the free version of Strelock on my android phone and it does everything I need. From my observation of a mate's pro version, it's just got more things to tweek.

Interestingly, I have the Applied Ballistics app on my iPad and it's free. Ballistics AE, on the other hand, has to be paid for, but it does do a nice job.

I must admit I don't use Strelock as much as I used to because I now DOPE my plot sheets for trends at all known distances. It's only when I use a new load or shoot at a new distance (Orion for example) that I refer to it.

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Strelok+ probably has everything you need, it has the Hawke half mil reticle, zooming, different target types etc.

 

I think all you get extra on Strelok pro is the ability to use a variety of, and even customise, drag functions, and calculate spin drift and coriolis effect. but that is pretty esoteric stuff for a HMR trajectory.

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Thanks for the replies guys

 

My reticle is definitely not on my free version but there is a couple of other half mil dots I use, don't know if this matters as I've swapped between them and the calculations don't change, and I've never looked at another one to compare, maybe I have an old version. Like I said in the first post it's about spot on with a .22lr but not much good with my .17hmr which is a shame.

 

I'm not even sure about my BC really...does 0.125 sound about rite for a 17 grain federal with vmax bullet? All I know is it's zeroed at 100yds and at 150 I need to hold .75 mil dot and if I go to 200 i would need to hold 1.75 mil dot

 

Thanks again

 

Towsey

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Cheers for that, that's one thing sorted...provided that a 20" barrel with mod is similar to their 24", hmm

 

Towsey

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If you don't know your muzzle velocity you are mostly stabbing in the dark anyway.

 

Strelok+ has a feature to calculate the muzzle velocity from a range and drop, a bit approximate maybe but if you can shoot and measure that accurately (the range and zero range will have to be very accurate) it will give you a trajectory which is spot on, at 2 ranges at least!

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Yeah cheers for that, I think I've found a local shop with a chrono that will let me fire 10 shots or so to get an average

 

Does pro have the same feature if I buy that

 

Towsey

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I had to put in actual drops to get a corrected MV do this at as far as you can if you have an accurate MV still do the test but tweek the BC

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It's not just me then haha.

 

Do you mean on + or pro you can tell it where it impacts at wot range and it works that way, sort of backwards way round

 

Cheers

 

Towsey

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Don't forget that when measuring MV using an optical chrony, usually set between 2 to 4 metres from the firing position, you will only get an approximation which will be below actual MV (sometimes by a surprising amount) so unless using something like a Magneto speed, you have to fine tune MV by entering Chrony averaged data from at least a 10 shot string for your rifle zero'd at 100 yards, then shoot a 5 shot (minimum) group at 200 and measure to the centre of the group from the aim point. It helps to make the aim point as small as possible for both 100 and 200 groups. The distance from point of aim to point of impact for 200 is then entered as the drop on Strelock at 200yds, and MV adjusted accordingly so you get back to your 100yd point as zero. You now have an accurately calibrated drop chart from Strelock for your load/factory cartridge

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Don't forget that when measuring MV using an optical chrony, usually set between 2 to 4 metres from the firing position, you will only get an approximation which will be below actual MV (sometimes by a surprising amount) so unless using something like a Magneto speed, you have to fine tune MV by entering Chrony averaged data from at least a 10 shot string for your rifle zero'd at 100 yards, then shoot a 5 shot (minimum) group at 200 and measure to the centre of the group from the aim point. It helps to make the aim point as small as possible for both 100 and 200 groups. The distance from point of aim to point of impact for 200 is then entered as the drop on Strelock at 200yds, and MV adjusted accordingly so you get back to your 100yd point as zero. You now have an accurately calibrated drop chart from Strelock for your load/factory cartridge. You can alternatively tweak the BC figure (or both) so that the drop chart you create calibrates accurately against tested groups at the various ranges you'll shoot.

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It's not just me then haha.

Do you mean on + or pro you can tell it where it impacts at wot range and it works that way, sort of backwards way round

Cheers

Towsey

I have Pro its called Trajectory Validation usefully if you don't have a chrono and factory ammo speeds can be off plus I have a 14" barrel so is slower than std any way

 

Or as I say if you do have chrono you can tweek the BC instead.

 

Did mine at 200yards gives a corrected MV for me of 2331fps

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Cheers for that

 

Il have to buy pro and give it a go. I've been playing with different things on standard strelok like MV, BC and even scope height and I can get it near or even spot on at one range but not for all

 

It's zeroed at 100yds. At 50 it's about 10mm out then at 150 it's 0.75 mil dot and at 200 it's 1.75 mil dot but I can't get it right for those and all other ranges in between. It's looks so easy and accurate on YouTube haha

 

Thanks

 

Towsey

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Towsey, any balllistic calculator can only be accurate within the distances there is actual very accurate real fire information,if there has been any truing u (fiddling) with BC etc. SO if you have accurate MV (see below) and accurate drops at say 100y (you need about ten shots to get a reasoonably accurate centre for the drop,then should be fine to 100....ditto150 if similar accurate drop value.

17HMR is shedding velocity very fast,so sensutive to small input errors.

Varm points out even the distance to chrono will matter...you can at least reduce any error as follows:

Hornady 17 Vmax ammo is supposedly 2550fps at muzzle,and by 100y this has reduced to 1902 fps ie a loss of 648 fps (24"barrel).

Say your chrono is 9 feet in front of muzzle,that's 3 yards

3 yards in 100y is 3%,so maximum velocity reduction at chrono is 3% of the 100y loss which is 3%of 648 fps ie 19.44 fps

 

So 19.44 fps lost in first 3 yards (but actual loss will be a bit less-velocity is lost faster as distance increases) so maybe call it 15 fps so add that to your chrono readings to get a truer MV-by allowing for the 3% loss for the 3 yards from muzzle -approx of course,but 3% error will not help,and this reduces it to way under a half % (bettter than chronos +/- accuracy).

 

On published data from the H17HMR vmax 100 zero, is velocityfps and drop/drift" in 10mph wind:

 

Muzzle 2550 -1.5/0; 25y 2378 -.5/.2; 50y 2212 +.2/.8; 75y 1902 0/3.3; 125y 1757 -.9/5.3; 150y 1702 -2.6/8; 175y 1582 -4.7/9.9; 200y 1470 -7.8/13.4

 

That's the SAAMI manufactured specs-individual rifles may vary a bit-esp as that is 24" barrel -but gives some idea of comparative performance at distances. 20g loads at 2375fps,are close to 17g ones until 100y ,then add an inch to drop/drift beyond 100y.

 

As ever,however,check bu actual careful 10 shot real range firing-which gives accuracy limits too.

 

gbal

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Thanks for that info

 

Il wait for my new phone then just buy pro I think for the price, not that I know the differences but at least il have all it has to offer for the future, then ask to use the chrono at the gun shop. So will it help if I get an average MV for, say, muzzle-50-100-150-200yds...can all this be entered/used to my advantage? Can I ask, why is the chrono set up slightly in front of and not actually at the muzzle?

 

Thanks

 

Towsey

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Towsey, not sure if a velocity reading at 200y etc is really feasible-the drip drift is 8/15 and space between screens is'nt (inverted Vs usually) isn't that generous !

What is best is accurate MV,and drop datafrom a good sample of shots- 200y would be fine,if do-able-ideally ,at the max plausible useage range (which isn't likely to be more than 200y)-then any error out to that anchor point will be neligible (given good data input)-far better ten shots and accurate group centre drop at intermediate distance than ,say,3 sshot approximations at several distances-'approximate' is a bad word for calibration!

 

Placement in front for screen chronos is to "ensure' bullets go through screens,but not contaminated by muzzle blast effects etc. (magneto is immune from such effects,and labradar depends on them,and sound-slightly behind muzzle,actually-essentially giving actual MVs....the screen chronos need a small correction -as described-as they are a few feet downrange,and rf velocities are not that high (though a smaller correcton is still adviseable for CFs

 

Note-you will have about 5x wind 10mph drift compared to drop at125y (5 inches,1 inch) but accurate ranging is still important (with a 100 y zero,drop from 125 to 175 is .9 to 5.1) so a laser RF is indicated.

 

g

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Yeah that makes sense, to be honest the groups are surprisingly good at 200 and it often get used out past that in 2 particular places but that's in low or no wind and definitely not gusty...that could get expensive with the chrono down range but I just thought I'd ask haha.

 

I'm using federals at the mo which reckon to be 2530 MV and I'm on a 20" barrel with mod so we shall have to see wot it actually is with the correction applied (thanks for that explanation aswell) and my drop at 125/175 is 1.5/7.5. If I can't get any joy il just have to go back to the old ways, at least they don't suffer from flat batteries and the like ha.

 

Many thanks

 

Towsey

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Towsey,glad it was helpful. It can be interesting to actually put real figures on velocity effects etc....often the actualpractical effects are rather small....lets see....100y zero

 

Fed 17g Vmax @ 2530 fps drops/drift at 125 1.0//4.9 and at 175y 5.2/10.3

Horn 17 Vmax @ 2550 fps " ' 125 .9/5.3 ' 175 5/ 11.3

 

OK,that shows that 20 fps MV loss has a very small effect at 125 yards ,and 175 y maybe an inch windage...

 

Your barrel is 20 ",above is standard SAAMI 24";you will lose (in the 2500-1500 fps range) about 5fps/" so about 20 fps for 20" barrel.

It's fairly clear that won't have much effect-pretty much the same as the (2550-2530) effect-negligible at 125,lets say an inch+ windage at 175compared to the Fed 17@2530 figures ......individual rifles etc will vary a little too,and mods etc .

 

Your 125 drop is 1.5,which seems OKish,but you are dropping a bit more by 175 if your drop is 7.5. That may well be correct,I'd check it with 10 shots-especially as you might want to shoot at 175-200 in good conditions....minute of bunny comes into play.

 

A good ballistic program is a real help- though a laser rangefinder is essential,and no wind highy advantageous (kestrel is muzzle only,but that helps a bit ). But yeah,charge batteries first. Or,old tech-write the calculated values for distances on a card as back up.

....wind is usually the challenge whatever tech is deployed,as you know.... :-)

 

g

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